The neurotransmitter dopamine has been implicated in cognitive control and working memory. Specifically, the D2 dopamine receptor agonist bromocriptine has been demonstrated to affect task switching and resistance to distraction in visual working memory. Here, we systematically manipulated spatial attention in a cueing paradigm and assessed the effects of bromocriptine administration on behavioral performance. Subjects performed a visual discrimination task in which they reported the tilt of a target grating that appeared in one of four locations. Each trial began with the presentation of a cue in one of the four locations. Voluntary and involuntary attention were separately assessed by manipulating cue probability and cue-to-target stimulus onset asynchrony (SOA). Some blocks were anti-predictive: for 20% of the trials, the target appeared in the cued location. In the remaining 80% of trials, the target appeared in the location diametrically opposite the cue. In other blocks, the cue was not predictive of target location (target appeared in cue or other locations with equal probability). In addition, there were two SOAs: long (600 msec) or short (40 msec). In the predictive blocks, for long SOA trials, allocation of voluntary attention to the expected (opposite) target location resulted in shorter response times (RTs). When the SOA was short, the involuntary capture of attention resulted in the opposite pattern: RTs were significantly shorter when the target appeared in the same location as the cue. When the cue was non-predictive, only involuntary attention effects were observed. Bromocriptine was administered in a double-blind, placebo-controlled, crossover design. We found that bromocriptine enhanced the effect of spatial cueing (difference in RT for targets appearing at the opposite versus cue location) for long SOA but not short SOA blocks and only in the anti-predictive cue condition. This result demonstrates dopaminergic modulation of voluntary but not involuntary spatial attention.